Pet food calorie counts use a 1920s formula that underestimates actual metabolizable energy

Most pet food companies calculate calorie content using modified Atwater factors, a formula originally developed for human foods in the early 1900s, rather than performing actual digestibility feeding trials. This means labeled calorie counts can underestimate true metabolizable energy by 10-30%, so an owner carefully measuring portions based on kcal/cup is still overfeeding their pet without knowing it. The problem persists because AAFCO allows the calculated method as an alternative to expensive feeding trials that cost $30,000-$50,000 per product, the vast majority of manufacturers have never validated their calorie claims against actual dog or cat digestion data, and there is no penalty for inaccuracy as long as the calculation methodology was followed correctly.